This invention relates to coloration of synthetic resins, and more particularly to the provision of weatherable resins which are blue in color.
With the ever-expanding areas of use of synthetic resins and especially thermoplastic resins, it is of increasing interest to produce resinous compositions having many types of surface appearance, including coloration. In particular, the production of resins which are blue in color is a concern.
Coloration of resins can be achieved by the use of dyes or pigments. One of the characteristics of pigments is their insolubility in the resin phase, which can lead to adverse consequences including loss of physical properties and loss of surface gloss. It is often preferred, therefore, to employ dyestuffs for coloration since they typically dissolve in the resin, forming a homogeneous composition which retains the gloss and advantageous physical properties characteristic of the neat resin.
The original industrial development of dyestuffs in the 19.sup.th century had as its goal the coloration of fabrics. It was necessary, therefore, to provide molecular features in the dyestuffs which maximized their adhesion to the fabric fibers. This often requires the presence of highly polar groups. For example, two commonly employed blue dyestuffs are Disperse Blue 60, or 1,4-diaminoanthraquinone-2,3-dicarboxylic acid N-(3-methoxypropyl)imide, and Amaplast Blue R3, or 1,4-bis(2,4,6-trimethylphenylamino)anthraquinone. The synthesis of such dyestuffs is complex and expensive. It would be desirable to develop blue dyestuffs having simpler molecular structures, not requiring as complicated a synthetic pathway.
Another factor of concern in the coloration of synthetic resins is weatherability. Many such resins undergo photoyellowing and/or loss of gloss over time. For example, polycarbonates are often severely yellowed when exposed to outdoor conditions and particularly when exposed to ultraviolet (UV) light. The photoyellowing phenomenon is, naturally, accompanied by undesirable color change in a colored resin.
One way of protecting a resinous article against the effects of weathering is by the use of a weatherable polymer such as resorcinol isophthalate/terephthalate. Said weatherable polymer may be employed in bulk for the fabrication of the article. More often, however, it is used as a weatherability-improving additive or as the outer layer of a multilayer article. Alternatively, a copolymer comprising weatherability improving units may be produced; such copolymers are exemplified by block copolyestercarbonates containing 2,2-bis(4-hydroxyphenyl)propane (hereinafter sometimes "bisphenol A") carbonate blocks in combination with resorcinol isophthalate/terephthalate blocks.
It is of increasing interest, therefore, to produce resinous articles having a blue coloration. It is of further interest to produce such articles having a high degree of resistance to weathering and the color changes caused thereby.